How to get browser information in PHP?

PHP provides to get browser information by function. Below is the simple example.
 

<?php
echo $_SERVER['HTTP_USER_AGENT'] . " ";
?>

Above example may display as following, if you use FireFox.

Mozilla/5.0 (Windows; U; Windows NT 5.1; ko; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3 ( .NET CLR 3.5.30729) 

In order to get above variable on function, you need to declare on top of the function as below.

function foo()
{
  global $_SERVER;

  echo $_SERVER['HTTP_USER_AGENT'];
}